A new surface characterization technique: RIMAPS (Rotated Image with Maximum Average Power Spectrum).

This work introduces a new imaging technique, Rotated Image with Maximum Average Power Spectrum (RIMAPS), for use in determining orientation and characteristics of surface topography. It consists of computing the maximum value of the averaged power spectrum, given by one step of the two-dimensional Fourier transform, for each angle of rotation of a digitized image. The basic measurement science of this technique is described and different cases are studied. The characterization of simple geometrical figures explains the meaning of peaks and their angular positions given by RIMAPS analysis. A known surface pattern made on a sample of pure copper, mechanically ground, is used to study reproducibility, dependence on image quality and topography scale relative to pixel size and magnification. Samples of pure zinc, mechanically ground and chemically etched, were used to show the main features of RIMAPS analysis when characterizing a more complicated pattern on a real surface. All the studies performed under different conditions for observation and acquisition of images give strong evidence of the stability and robustness of RIMAPS as a technique for the characterization of topography.

Linear rugosity concept of crystalline surfaces by using the unidirectional laser oblique illumination (ULOI) technique.

The study of the I(phi) curves obtained with Unidirectional Laser Oblique Illumination describes the roughness of a crystal as a combination of straight edges in different directions, which generate the concept of linear rugosity. In the present work, a model of the crystalline surface based on this concept is introduced. Diffraction gratings as well as metallic surfaces subjected to different metallographic procedures are analyzed. The theoretical results are compared with experimental values obtained in samples of Fe and Zn using an objective of 16x. Both values, theoretical and experimental, are in total concordance.

Theoretical analysis of lethal factors in plant populations.

In this article, we are interested in the problem of the existence of a few linkage groups in which lethal infertile genes associated with yield factors are present. This hypothesis is supported by the finding of natural balanced lethal systems, which keep a short heterotic chromosome segment. It is very important to predict the number of generations that a balanced lethal system maintains in its linkage, in order to get a permanent heterozygosis without any problem with recombination. For theoretical analysis we have used the theory of absorbing Markov chains, discrete in space and time, because this is well suited to crops like barley. It results from studying some experimental data obtained by Ewald A. Favret in the CICA, INTA, Castelar, Argentina.

Influence of Marker Genes on the Expression of Somatic Mutations in Barley.

Mutagenic agents have been evaluated in terms of their effects on germ cells. The study of induced somatic mutations is a faster, more economical, and less laborious method than the traditional ones. The induction of somatic sectors by x-rays, ethyl methanesulfonate, and sodium azide was studied in cultivated barley. Four stocks were used: a normal one, a balanced lethal genotype carrying two chlorophyll-deficiency genes of different expression (albina and golden), and two (semidominant) chlorophyll mutants of the same dominant gene, which in the progeny of selling segregate 1 normal green: 2 light green: 1 yellow seedlings. Treatments were applied to seeds, and the fourth, fifth, and sixth leaves of the main shoot were examined in the M1 generation for the presence of sectors showing conspicuous changes in chlorophyll content. Highly significant frequencies of dark green sectors were induced by all three mutagens in the (semidominant) heterozygous plants, whereas evidence of somatic crossing over or mitotic nondisjunction was very rare in this material and in the balanced lethal genotype. In all cases, the frequencies of induced sectors without chlorophyll were much higher in the heterozygotes than in the normal homozygotes, with each mutagen showing typical dose-response curves. A notable interaction between mutagen and genotype was found. The variation in the relative frequencies of sector types in the various genotypes points to the differential influence of the marker genes.